1. Field of the Invention
The present invention relates to a reactive blue dye, and more particularly to a reactive blue dye represented by the following Formula 1, which is effective in black dyeing or printing of polyamide textiles, in particular, nylon fiber. 
In Formula 1, M is a hydrogen atom or an alkali metal atom.
2. Description of the Related Art
Polyamide textiles, especially nylon fiber, have drawn much attention as a material for sportswear. In general, acid dyes are used for dyeing or printing of nylon fiber. However, when acid dyes are used for heavy color dyeing, the result of washing fastness becomes poor. Binders are often used to solve this problem, but they have drawbacks such as high cost and the deterioration of touch. Metal complex acid dyes used for high light fastness are undesirable in terms of environmental contamination related to heavy metals.
Japanese Patent Unexamined Publication No. Sho 43-15299 discloses an H-acid derived monofunctional disazo blue dye, which is nobtained by diazotization of 4-aminophenyl-β-sulfatoethylsulphone represented by the following Formula A. 
In Formula A, M is a hydrogen atom or an alkali metal atom.
Since the 4-aminophenyl-β-sulfatoethylsulphone substituted monofunctional blue dye is highly soluble in water, it is separated by salting out using a large amount of salts. In the process, wastewater contaminated with the concentrated dyes and salts is generated. When this dye is applied for dyeing, the dyeing efficiency is poor because of the low substantivity of the dye as well as the concentrated wastewater of the unfixed dyes is generated, thereby increasing the cost for the wastewater treatment. Also, due to the increasing demand on the use of liquefied dyes considering workers' health and automation of dyeing processes, a concentrated dye with low salt content is highly required.
As another blue dye, 4-aminophenyl vinylsulphone (Formula B) substituted dye is reported [Ho Jung Cho and D. M. Lewis, Coloration Technology, 2002, 116, 198-204] to be less soluble in water than the 4-aminophenyl-β-sulfatoethylsulphone (Formula A) substituted dye, it is more advantageous in salting out. In fact, because no salt is added during the separation of the 4-aminophenyl vinylsulfone (Formula B) the salt content of the wastewater can be reduced. 
Moreover, since the obtained dye contains less salt, the salt content of the dyeing wastewater can be reduced, and the desalination process to obtain a liquefied dye becomes simpler.